Blood Lecture - Anatomy & Histology PDF

(Histology of) BLOOD Anatomy, Histology and Embryology-I Oral Anatomy, Histology and Embryology-I Krisztina Holló PhD  BLOOD a fluid connective tissue Transport of O2, CO2 Transport of nutrients, metabolites Delivery of hormons and other...

(Histology of) BLOOD Anatomy, Histology and Embryology-I Oral Anatomy, Histology and Embryology-I Krisztina Holló PhD  BLOOD a fluid connective tissue Transport of O2, CO2 Transport of nutrients, metabolites Delivery of hormons and other regulatory substances Maintenance of homeostasis (buffer, thermoregulation, blood clotting) Transport of humoral agents and cells of immune system Blood is the most common biologic fluid collected for clinical laboratory testing. It is usually drawn from a vein (in the arm) directly into an evacuated tube. Typically, a tube will hold about 5 mL of blood – enough to perform many clinical chemistry tests, since automated analyzers require only small amounts (usually from 2 to 100 μl) for a single test. Occasionally, when collection of blood from a vein is difficult, a sample of capillary blood may be collected by pricking the skin and collecting several drops of blood from the puncture site. An example is the use of heelstick blood for testing of newborns. (Clinical Chemistry, Abbot) Fractionation of blood components Hematocrit (HCT): volume of packed erythrocytes in %. Normal value: ~ 45%  90% water, ~55% 8% protein, Erythrocyte FORMED 1% inorganic salts, Leukocyte ELEMENTS BLOOD- 0.5% lipids, PLASMA 0.1% glucose Thrombocyte ~45% and other minor components. plasma formed elements Blood smear (May-Grünwald-Giemsa staining) Examination of blood cells in blood smear. counting the number of different types of blood cells Traditional method: Bürker chamber (haemocytometer) Haematology Analyser  Complete Blood Count (CBC) (quantitative blood count) Number of formed elements in a volume unit of blood ERYTHROCYTE  4.5 – 5.5 T/l (red blood cell, RBC) THROMBOCYTE  0.15 – 0.3 T/l (platelet, Thr) LEUKOCYTES  4 – 11 G/l (white blood cells, WBC) G= giga, 109; T = tera, 1012  Erythrocyte (red blood cell, RBC) Anucleate cells typically missing cellular organelles also Biconcave disc shape Provides maximum cell surface – important feature for gas exchange Diameter: ~ 7.2 – 7.8 μm (can be used as a histologic „ruler”.) Life span: ~ 120 days Normal number: 4.5 – 5.5 T/l  Erythrocyte Capillary structure Special cytoskeletal network and cell membrane - flexible cell shape, allows the passage of RBCs in small capillaries Erythrocyte Transport of oxygen and carbon dioxyde Normal RBCs in blood smear Hemoglobin:  95% of RBCs proteins  binds oxygen Sickle cell anemia (blood smear) Point mutation in the gene encoding hemoglobin Erythrocyte Erythrocyte membrane contains blood group antigens. Blood transfusion e.g. AB0 Blood group system  EM 18000x Platelet Thrombocyte Diameter ~ 2 - 4 µm Cytoplasmic fragments of megakaryocytes Life span: 7-12 days Normal number in peripheral blood: 0.15 – 0.3 T/l Removal of aged forms: spleen, liver Platelet The ɑ (alpha) granules contain bioactive substances e.g. mitogen growth factor thrombospondin adhesion molecule von Willebrand factor heparin neutralizing factor etc. The dense (δ) granules contain Serotonin, ATP, ADP, Ca 2+ , Mg 2+ Upon injury of the vessel wall when the endothelial Peripheral: hyalomer zone lining becomes damaged it initiates a complex Central: granulomer zone biological process which results in blood clotting (haemostasis).  Thrombocyte release reaction: Upon injury of vessel wall – platelets get in contact with connective tissue molecules (collagens), Thrombocyte aggregation is triggered by collagen Release of granule content OpenClass  Thrombosis Blood clotting can occur in intact blood vessels Thrombosis is when a blood clot (thrombus) forms within a blood vessel and prevents the correct flow of blood around the circulatory system. There are two components to a thrombus: aggregated platelets and red blood cells that form a plug, and a mesh of cross-linked fibrin protein. Differential (blood) count WBC differential Percentage ratio White blood cell count of leukocytes Qualitative blood count Normal ratio of leukocytes Neutrophil granulocyte ~ 60-70% Lymphocyte ~ 20-40% Monocyte ~ 3-8% Eosinophil granulocyte ~ 2-4% Basophil granulocyte ~ 0.5% Band (stab) ~ 1-2% Juvenile (jugend) ~ 0.5% Leukocytes (white blood cells, WBC) Granulocytes Agranulocytes Azurophil granules Specific granules Azurophil granules Leukocytes (white blood cells, WBC) Granulocytes Azurophil (primary or non-specific) granules: lysosomes Specific (secondary) granules: Neutrophil Eosinophil Basophil Specific granules Azurophil granules  Leukocyte extravasation The white cells in blood are a cell population in waiting, a reserve pool. When stimulated by chemotaxins and aided by expression of leukocyte receptors on the endothelial cells, the blood leukocytes exit into tissue and become part of the inflammatory process. Numbers in blood might be expected to fall as a result, but a number of mature granulocytes are ready to respond, attached to the lining of small vessels. These form a functional reserve, not included in the blood count, but rapidly mobilised by the chemotaxins and cytokine signals of inflammation. Leukocytes can migrate through the wall of postcapillary venules (extravasation) Leukocytes appear both in blood and connective tissue. Upon chemoattractant signals they migrate to sites of tissue damage or infection. Neutrophil granulocyte Diameter ~ 10-12 m Segmented nucleus (3-5 lobes) – show dynamic changes Life span: 7-12 days Ratio in peripheral blood (differential count): 60-70% GRANULES: Azurophil (primary, non- specific) granules: primary lysosomes contain hydrolitic enzymes Specific (secondary) granules: small-sized, spherical granules contain antibacterial agents (lysosime, phagocytin etc) and enzymes.  Neutrophil granulocyte, neutrophil segment, polymorphonuclear cell, polymorph Secondary or specific granules Primary or azurophil granules Lysozyme, gelatinase, collagenase, Are lysosomes lactoferrin, cathelicidins, Myeloperoxidase transcobalamin I etc. Neutrophil defensins etc. Neutrophil granulocytes Anti-bacterial function Phagocytosis Degranulation Nettosis Eosinophil granulocyte Diameter: 12-14 m Bi-lobed nucleus Life span: 8-12 days Normal ratio in differential count: 2-4 % GRANULES: Non-specific (azurophil): (lysosome) lysosomal acid hydrolase etc. Specific: crystalloid bodies - major basic protein, histaminase, kollagenase, cathepsins The eosinophil granulocyte is capable of extracellular killing of parasites (e.g. worms) by releasing its granule contents Eosinophil granulocyte, electronmicrograph crystalloid bodies In the core of the specific granules crystalloid structures are recognized with electron microscope. Its major component, the major basic protein (MBP) is rich in arginine, this feature provides the basic property of the molecule and accounts for the eosinophilic staining of the granules. Function in peripheral tissues: Antiallergic action (histaminase) Antiparasitic (MBP) Basophil granulocyte Diameter: 10-12 m Nucleus less segmented, covered by the basophilic granules Life span: 8-12 days Normal ratio in differential count: ~ 0.5 % GRANULES: Non-specific: lysosomal acid hydrolase (lysosome) Specific: heparin, histamin, leukotriens, interleukins Function in peripheral tissues: Allergic reactions Inflammatory reactions  Monocyte Diameter: 15-20 m Life span: months – years (not exactly known) Kidney shaped nucleus, deep indentation Azurophilic granules (lysosomes) in cytoplasm Normal ratio in differential count: 3-8 % Phagocytosis Professional antigen presenting cell Cytokine production Functions in peripheral tissues: Differentiate to macrophages (MPS = Mononuclear Phagocytotic System) Small lymphocytes Diameter : 5-7 µm Thin cytoplasm which contain azurophilic (non-specific) granules Life span: years (for memory cells decades) Normal ratio in differential count: 40-60 % T-lymphocyte (thymus-dependent) Major populations: helper, cytotoxic, memory and regulatory →Function: cellular (cell-mediated) immunity B-lymphocyte (bursa, bone marrow–dependent): differentiate to antibody- producing plasma cell or B memory cells →Function: humoral immunity Antigen dependent adaptive (acquired) immunity Large, granular lymphocytes Diameter ~15 µm Numerous azurophilic, large granules in the cytoplasm ~ 5-10 % of lymphocytes Natural killer / NK-cells / null cells Recognise and kill tumor and virus infected cells Natural (innate) immunity  „Left shift” of blood count A left shift indicates the presence of immature cells in blood and usually, but not always, indicates an inflammatory leukogram. Immature neutrophils are usually band If the demand is sufficiently extreme, metamyelocytes and myelocytes are also mobilised into the circulation and hence neutrophils, but earlier into the tissues; this has been called left shift. The alternative forms can be seen in of increased maturation is called right shift but is not some cases. commonly seen. The normal development process in marrow from myeloblast to myelocyte takes 6 days and from myelocyte to release of neutrophil into blood another 7 days. Production is driven by a range of growth factors and cytokines, including G-CSF, GM- CSF, IL-3, and IL-5. Literature Wheather’s Functional Histology W Pawlina, MH Ross et al: Histology. Text and Atlas M Petkó et al: Histology LP Gartner, JL Hiatt: Concise Histology Scientific papers Figures, pictures freely available on the internet